509 Aluminum Big Block Engine Build - W=Wow!

Lamar Walden Put Together The First Of His All-Aluminum W-Motors And We Were There.

Like a lot of other segments in our hobby, the legendary 409 is enjoying a new heyday. The beginning was about 10 to 15 years ago when stroker kits hit the scene, punching displacement up to 482 ci. Within the last four or five years, strides have been made with aluminum heads, dedicated distributors, reproduction and aftermarket oil pans, roller cams and roller rockers. Leading the charge since running a blown and injected 409-powered '33 Willys in the early '60s has been Lamar Walden.

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From billet blocks to rocker arms, Walden has made just about everything possible for a 409. His most recent venture has been to team up with Bill Mitchell at World Products to develop an aluminum 409 block.

"The problem is that blocks have just about dried up," Walden says. "You can get race or street heads and intakes, billet timing chains, valve covers, crank kits, good pistons, and everything else. The only thing you can't get-and the most important-is the block."

There were originally two factory blocks: passenger car and truck. The truck blocks are the most common, but have a handicap in the form of a large, compression-killing notch cut in the side of the bore. Opinions vary on "The Notch." Over the years, it's been said the notch unshrouds the exhaust valve, which is true. However, the benefit of the unshrouded valve usually doesn't outweigh the compression drop. It's good for a forced induction application, and some race engines. Prices for buildable passenger car blocks range from $2,500-$4,000 (and cracked cylinder walls or water jackets aren't deal breakers), while truck blocks aren't far behind.

As much as we love the '09, we have to be honest and admit there are several shortcomings: The deck is a little on the thin side, making high/race compression ratios, forced induction or nitrous a dicey proposition (flex does bad things to head gaskets). They also have a tendency to pull head bolts out. The area where the exterior of the block meets the deck is also thin-Walden has dozens of blocks that were cracked from running too hot or freezing. (Fortunately, he's developed a method of repair).

And then there are the 409-specific bits that can add hundreds of dollars to a build: oil pan, timing cover, distributor (or spacer sleeve) and harmonic balancer. Reproduction oil pans are in the neighborhood of $300, while original timing chain covers are scarce. And you need the right one, because there are two timing tab locations.

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509 Aluminum Big Block Engine Build - W=Wow!

The first aluminum 409 block out of World Products' foundry. Walden got the first two samples to make sure everything was in the right spot before World went into full production. This block needed a few revisions, like prototypes always do, but it was about 98-percent "there."

The World aluminum block comes ready to assemble. That's a big deal when figuring in the cost to refurbish an original iron lung. Walden made sure the World block was reinforced and beefed up in critical areas that were lacking on original 409 blocks.

Standard on the World block are beefy splayed 4-bolt main caps, a necessity when building a stroker big-block. Main journals are standard big-block Chevy spec.

Not all the 509 blocks will be machined for O-rings, but Walden machined this one to reinforce the prototype copper head gaskets.

Note the ridge: Below the ridge is the cylinder bore, above the ridge is the combustion chamber. That ridge is critical to 409s-without it, the rings pull carbon deposits down into the bore, wiping out the rings, bores and piston skirts. Most machine shops don't realize this, never mind being set up to put it back after boring the cylinder.

Geneology of the 409 piston: far left is a stocker, the middle shows one of Walden's custom-made stroker 482 slugs (note the raised pin height and less overall mass), and on the right is the latest offering for the World 509 block: much taller pin-height, considerably less mass. The 509 comes with a 4.500-inch bore, while stock 409 is 4.3125-inch. Race pistons are even more radical.

This engine received a set of Walden's pistons, with a 10.5:1 CR, and 0.250-inch longer Eagle big-block Chevy rods.

Cam choice is a solid roller, ground by Comp. The 409 cam is the same length as a BBC, but the valve layout is SBC, requiring 409-specific cams. Lamar has his own part number in the Comp catalog, but it's pretty much a blank-lobe profiles are cut for each application. Ask Lamar what the specs are, and he'll tell you, but after a while you'll realize he never really got around to saying, exactly.

Crank is an Eagle 4-inch stroker big-block unit, up from the stock 3.50-inch stroke. The rotating assembly has been balanced. Any time we follow along on an engine build with the Waldens, we like to make Rob hold the crank up in the air while taking our sweet time shooting pics. He likes that.

Note the valve reliefs in the pistons-they have to go into the block in the correct order and orientation.

Here's the big deal with 348/409 engines: the combustion chamber is in the block. The inboard side of the piston comes up flush (or very nearly) with the deck/bottom of the head. The wedge-shaped area on the outboard side is the combustion chamber. The bottom of the cylinder head is flat, as you'll see in a moment. That wedge is why the deck is not at 90 degrees to the bore.

Even with custom-spec'd parts, every cam is degreed.

This is the first set of copper head gaskets Walden had sourced for the big-bore W-engine. Because of the deck's angle, the bore hole for the gasket is oblong, rather than perfectly round.

The aluminum block and head combo was secured with ARP head studs.

Walden has been making aluminum street heads based off the high-performance factory castings for a while, and still had the prototypes in his shop.

Besides the odd shape of the valve covers, the bottom of the head shows the lack of combustion chambers, and the SBC valve layout. The heads were fitted with 2.25-inch intake and 1.72-inch exhaust valves, with the intakes flowing more than 350cfm at 0.700-inch lift.

Stock 409 rocker arms were 1.75 ratio. For valvetrain stability on his high-performance, aluminum-headed engines, Walden designed these pedestal-mounted full-roller rockers. These retain the stock ratio.

The rocker pedestal boss on the head is machined for the dowel to locate the pedestal, which is secured by the rocker bolt.

Note the funky angles of the rocker arms. Walden's -690 heads are based on the factory 425-horse street heads, but have had improvements made to the valve location and ports, influenced by the factory Z11 heads.

Walden's billet timing chain cover, with integral cam button, was installed. Big-block Chevy and 409 timing covers aren't interchangeable, but they are on the new aluminum block, opening up the possibilities for much easier-to-find BBC covers, and readily-available belt drives and crank-trigger ignition systems.

Nothing looks like a 409 water pump, and keeping that unique piece was a prerequisite for the aluminum block, though a standard BBC piece would have been less work in the design phase. Walden has had his own aluminum pumps cast for years, with a reinforced bearing housing.

After the aluminum 509 block was announced, Hilborn contacted Lamar and wanted to do a retro fuel injection unit. The Hilborn unit has bosses for mechanical or electronic fuel injection, and three sizes of butterflies. This is the first, and uses 2.5-inch butterflies, 60-pound injectors, and is controlled by a FAST computer system and distributor. The 3-piece intake (injector banks and a separate valley cover) was powder coated black.

Finishing the prototype engine is a new serpentine belt-drive system. Unlike other systems on the market, this can be tailored to mount any combination of power steering, A/C, or dual alternators, without a bunch of additional "dummy" idlers. Lamar reversed the water pump to work with these. Note the humped spokes in the pulleys, inspired by the valve cover's shape. This set-up was hours old when we shot it, and wasn't completely finished.

We transform our 348ci Big-Block engine to a 434ci stroker and show you step-by-step how it's done. Only at www.chevyhiperformance.com, the official site for Chevy High Performance Magazine. » Read More